Water often and deeply, soaking the soil six to eight inches deep at least twice a week. Tomatoes do not respond well to letting the soil dry out between waterings. Keeping moisture levels in the soil even will help prevent the dreaded blossom-end rot, that small black spot on the bottom of the tomato which eventually can spread throughout the fruit.
A layer of mulch (straw, plastic, grass ) will help conserve soil moisture during the hot, dry days of July and August. In addition to moisture, tomatoes need warm soil. Black plastic mulch will work wonders if you live in a land of cool summers. For people in warmer climes, straw or another organic will be your mulch of choice.
Note: There has been quite a buzz lately over using red plastic mulch to improve tomato yields and reduce the number of days to harvest. Early research, conducted by the USDA and Clemson University, found that tomato plants grown over red mulch produced about 20% more fruit than those grown over black plastic. Another study conducted by Montana State University found no difference in the color of mulch used and total yield, but did show that red mulch hastened ripening. Many other studies have been performed to determine the benefits of red mulch … all with varying results. It’s our opinion, that if you’re out to grow the best tomatoes in the neighborhood, then it’s probably worth a try!